1. Field of the Invention
The present invention relates to a storage medium having a plurality of storage areas distinguished by stored data such as a format, etc., and to a technique for playing back data stored in the storage medium.
2. Description of the Related Art
In recent years, remarkable progress in information compression technology and in semiconductor technology has been made. For example, the international standards such as MPEG 1 and 2 have been made, so that standards for storage media for storing information are frequently revised. Recently, the standardization of DVDs (Digital Video Discs) has been completed. For CDs (Compact Discs), multimedia-conscious standards are frequently proposed. A CD which is conscious of multimedia is called being an enhanced CD.
The enhanced CD includes two storage areas distinguished by data format. One area is for storing the same CD-DA (Digital Audio) data as that of a conventional music CD, while the other is an area for storing CD-ROM data. Image data (including data encoded with the MPEG encoding method) such as a promotional video, record jacket, etc., can be stored as the CD-ROM data. Therefore, the enhanced CD attracts public attention as a tool for providing entertainment over and above the conventional music CD.
As is known, enhanced CDs are classified into three major types depending on their format. The first of these types is called mixed mode, the second is called multi-session, and the third is called CD-ROM ready. The multi-session type can store CD-DA data in tracks 1 through 99 in a similar manner as in a music CD, unlike the other types. It allows a conventional music CD player to play back music. This is the reason why the multi-session type is of the greatest interest to the general public. The multi-session type is normally called a CD-EXTRA.
In the meantime, the number of personal computers (hereinafter abbreviated to PCs) has been remarkably increasing in recent years, and PCs have been equipped with a CD-ROM device as standard. The PCs equipped with the CD-ROM device can only use a CD-EXTRA (enhanced CD) by adding the MPEG decoding capability. The number of PCs equipped with the MPEG decoding capability as standard has also been growing in recent years. Therefore, the number of CD-EXTRAs (enhanced CDs) sold for PCs is expected to significantly increase.
Because PCs are equipped with a CD-ROM device as standard, a device for accessing a DVD is expected to be included in PCs, by adding a capability for accessing a DVD in addition to a capability for playing back a CD-ROM (including an enhanced CD), etc.
The enhanced CD such as the above described CD-EXTRA, etc. allows high quality sound and a variety of videos to be enjoyed in a similar manner as with a music CD. Conventionally, sound and video are played back by basically reproducing data sequentially read from a CD. In other words, data of various representation media such as video (still pictures, moving pictures, photos, etc.), music, etc. can be recorded, but those data are not fully utilized. The same thing is said about storage medium other than the enhanced CD.